Eastern Ezo Nanbu Clan Jinya Ruins / Mororan Jinya Ruins /

Why the Shogunate Looked North

From the late eighteenth century onward, the seas around Ezo were no longer empty. Russian expeditions probed Sakhalin and the Kuril Islands; American whalers and warships ventured ever closer; and after the 1854 Treaty of Kanagawa opened Japan to foreign trade, the prospect of unauthorized landings became impossible to ignore. In April 1855, the shogunate divided coastal defense duties for Ezo among five northern domains — Sendai, Akita, Nanbu, Tsugaru, and Matsumae. The Nanbu Domain, whose seat was at Morioka in present-day Iwate, was assigned the long stretch of coastline from Cape Esan in the south to Horobetsu in the east, a sweeping arc that included the strategic harbour of Muroran.

The Nanbu response was swift and structured. A senior official named Niitobe Jūjirō — better known to history as the father of the famed Meiji-era thinker Nitobe Inazō — led a 28-member survey party to select sites. The plan that emerged placed the main camp (moto-jinya) at Yachigashira near Hakodate, with three outlying garrisons stretching east along Funka Bay: a substantial out-station (deha-jinya) at Pekereota near Muroran, and two sub-camps (buntonsho) at Oshamanbe and Sawara. Together, the three sites covered the western, northern, and eastern arcs of the bay.

Moroan Jinya: The Heart of Nanbu Defense

The Moroan Jinya, in present-day Jinya-cho in Muroran City, was the largest and most important of the three. Construction began in March 1856 (lunar calendar) and finished by September of the same year, an astonishing pace given the scale of the work. A team of eighteen carpenters led by Murata Sōkichi, four plasterers, five roof thatchers, forty earthworkers, and over forty-five woodcutters cleared and shaped the site, raising a square enclosure protected by a double ring of earthen ramparts and ditches.

About one hundred Nanbu samurai were stationed here at any given time, supported by batteries (daiba) at Poroshireto (today's Sakimori-cho) and Etomo, and by lookout posts at Oinaoshi and Washibetsu. The garrison was small but the responsibility was vast: from these earthen walls, the samurai watched the eastern entrance of the bay for any sign of unannounced foreign sails.

The end came in 1868. When the Boshin War spread north, the Nanbu Domain — having sided with the former shogunate — chose not to surrender the camp to the new Meiji government. In August of that year, the garrison set fire to the buildings themselves and withdrew to Morioka, leaving only earthworks, a few foundation stones, and an old well behind. From 1968 a five-year restoration project rebuilt the ramparts and ditches, exposing building footings and a stone-paved path. Today the site is enveloped in cool green woodland and old cedars planted to shield the gunpowder magazine; in mid-May to early June the cherry trees bloom in pale clouds across the inner enclosure.

Oshamanbe Jinya: A Short-Lived Strategic Outpost

Set on a low terrace just behind the mouth of the Oshamanbe River, the Oshamanbe Jinya was conceived as a midway sub-camp between Moroan and Sawara — and as a guard over the inland road that crossed via Kuromatsunai to the Sea of Japan coast. Established in 1856, it was the most short-lived of the three garrisons. Once the Nanbu commanders realized that the shallow, gently sloping shoreline made it difficult for large foreign vessels to approach in any case, the camp's purpose evaporated. It was officially abolished in August 1857, dismantled by December, and its building materials were sent on to reinforce the Sawara garrison.

The site later served as a sports ground, and the area around the front of the enclosure was reshaped during construction work for the neighbouring Iinari Shrine. Even so, sections of the original earthen rampart still survive, set among quiet trees behind the shrine — a discreet but evocative trace of a defence policy that lasted barely a single year.

Sawara Jinya: Where the Square Walls Still Stand

The Sawara Jinya, in what is now Sawara 3-chome of Mori Town (until 2005, an independent municipality called Sawara), is the most visually striking of the three sites. Built between October 1856 and the following January, it formed a square roughly 66.6 metres east-to-west and 59.4 metres north-to-south, ringed by an earthen rampart about three metres high and an outer moat. Approximately fifty Nanbu samurai were posted here, with smaller watch points around the town and at the foot of the great Mount Komagatake volcano nearby.

Recent excavation work confirmed that the outer moat — long invisible from the surface — still survives buried just 0.8 metres below ground, with original dimensions of roughly six metres wide and two and a half metres deep. Above ground, the rectangular ring of earthworks, with breaks marking the front and rear gates on the north and south sides, remains remarkably intact. Walking along the top of the rampart, one can still feel the careful geometry of a defence that was simple, fast to build, and very nearly invisible from the sea — exactly the qualities the Bakumatsu situation demanded.

What Makes These Sites Significant

The three jinya were collectively designated a National Historic Site by the Japanese government — Moroan in May 1934, with Oshamanbe and Sawara added in 1974, when the combined name in use today was formally adopted. Their value is unusually multifaceted. Architecturally, they are among the best-preserved late Edo coastal earthwork fortifications in Hokkaido, illustrating how Japanese castle-building traditions adapted to the urgent practical demands of the Bakumatsu defense crisis. Historically, they document the shogunate's first systematic effort to assert coastal defense over the northern frontier, and the human reality of samurai families uprooted from the warmth of southern Iwate to garrison a coast many had never seen.

That human reality is part of why the Moroan site is especially poignant. Many of the young samurai posted there never returned home: some died of illness or the punishing winters, with one recorded grave belonging to a soldier just nineteen years old. A cluster of their tombs still rests behind the inner enclosure, near the old gunpowder magazine.

Visiting the Sites

The three sites are spread across the southern coast of Hokkaido and can be visited as a thoughtful day-long or two-day trip around Funka Bay, ideally with a rental car. The Moroan Jinya is reached by a short drive from JR Honwanishi Station on the Muroran Main Line and is freely open as a forested park; spring brings cherry blossoms, autumn brings vivid foliage. The Sawara Jinya lies about a ten-minute walk from JR Oshima-Sawara Station on the Hakodate Main Line, with parking nearby and a clearly marked entrance. The Oshamanbe Jinya is roughly a fifteen-minute walk from JR Oshamanbe Station and best appreciated in good weather, when the surviving earthworks read clearly against the surrounding terrain.

None of the three sites has restored buildings, and that is part of their charm. They are quiet places, often empty, where the wind off Funka Bay carries something of the loneliness the original garrisons must have known. Information panels in Japanese explain the layout; photographs of cross-sections and earlier excavations help visitors picture the original camps.

Around the Sites

Muroran offers far more than the Moroan Jinya alone. The dramatic cliffs of Cape Chikyū (Earth Cape) and the geothermal valley of Noboribetsu Onsen lie within easy reach, and the white suspension span of the Hakuchō Bridge across Muroran Port is a landmark in its own right. Around Oshamanbe, hot-spring resorts and the gateway to the Niseko region are close at hand, while Mori Town near the Sawara Jinya is famous for ikameshi (squid stuffed with rice) and offers superb views of the still-active Mount Komagatake. Combining the three jinya with a relaxed lap of Funka Bay makes for one of southern Hokkaido's most rewarding off-the-beaten-path itineraries.